1. Field of the Invention
This invention relates to electrostatic spray coating systems, and more particularly to switch means for electrostatic coating systems.
2. Prior Art
Electrostatic spray coating systems of the type in which this invention is employed are shown, for example, in U.S. Pat. Ser. No. 4,287,552, issued to Josef Wagner and Willi Huber, Sept. 1, 1981, the teachings of which are incorporated herein by reference.
In such systems, particularly in trigger operated systems, movement of the trigger controlling the coating spray valve also actuates switch means controlling the electrostatic circuitry. In hand-held units having manually actuated trigger means, the electrostatic circuitry includes components formed in a trigger guard. Those components may include a proximity switch which is activated in dependent response to positioning of an end of the trigger adjacent the trigger guard. Thus, when the rocking trigger is in the valve closed position with the free end of the trigger moved furthest away from the pistol grip or pistol handle, the proximity switch, in response to the presence of the trigger handle, will be disabled to a circuit breaking condition thereby discontinuing supply of high voltage power to the electrode adjacent the spray orifice. Movement of the trigger away from the trigger guard towards a spray valve opening position will cause the switch to close thereby establishing power output at the electrode.
Such trigger actuated switching is desirable in that it eliminates the necessity of additional manually operated switch means to control the on-off of the power supply to the electrode while assuring that the electrode power will normally be terminated when spraying is not taking place. Moreover, by use of a proximity switch or similar device, initial movement of the trigger can actuate the power circuitry prior to beginning to open the spray valve. This will assure that there is always an electrostatic field present during spraying.
However, it is sometimes desirable to utilize the coating spraying system without the electrostatic field. For example, in one sided coating the existence of an electrostatic field would provide a wrap around coating which would coat the opposite side of the piece being sprayed. In such instances it is therefore desirable to deactivate the electrostatic field. However, when spraying mixed articles where some spraying is to be done with the electrostatic field and some without, the operator is required to leave the immediate spray booth area and move to the main control for the electrostatic to either activate it or deactivate it. This can result in substantial time delays. It would therefore be an advance in the art to provide an electrostatic paint spray device having a trigger activated electrostatic circuitry switch with means at the spray device to prevent activation of the circuitry when desired irrespective of trigger movement.